How to build Safe Roofs with Corrugated Galvanised Iron (CGI) Sheeting
Corrugated Galvanized Iron or Steel (CGI or CGS) sheets are at present the best known, most widely available low-cost roof covering material. There is an enormous variety of qualities of CGI sheets on the market, greatly varying in the different regions of the world.
This manual aims to give guidance on how to choose the most suitable quality of CGI sheets for a given context and how to correctly handle and install CGI sheets as roof covering. Furthermore, the manual presents some maintenance and preventive measures that help to ensure the safety and durability of a CGI roof.
As this manual particularly focuses on improving safety and storm/cyclone resistance of roofs covered with CGI it provides some guidance on the most suitable roof form and pitch to withstand expected wind loads, in order to help make informed choices for a given context. In areas with a very low risk of strong winds, the focus on the high quality of CGI and strong fixings can be reduced.
The manual is structured into five sections:
- Section A: Materials and tools, focusses on CGI and the key performance specifications and present materials used for the roof structure as well as the different fixings and accessories and the tools needed when working with CGI sheets.
- Section B: Safety equipment and quality control, transportation and storage of CGI sheets and other items made of galvanized iron or steel.
- Section C: Design of the roofs (shape and pitch), explains how wind forces affect a structure and what measures (e.g. the shape of the roof) help to reduce wind pressure on the roof covering. Four different roof shapes and pitches are explored in different site exposures to identify the most suitable type for each situation.
- Section D: Installation guidance, gives detailed instructions on how to correctly install and fix CGI sheets. Example calculations based on wind speed and site exposure.
- Section E: Roof maintenance and preventive measures, explain how to maintain and repair CGI roofs and measures that can be applied (e.g. before a storm warning) to reduce the risk of roof damage by strong winds and cyclones.